JP5339288B2 - Perovskite oxide fluorescent thin film - Google Patents

Description

  The present invention relates to a perovskite oxide fluorescent thin film, and more particularly to a perovskite oxide fluorescent thin film in which a perovskite oxide fluorescent thin film having a large area is formed on a heat-resistant clay-based flexible sheet substrate.

  Conventionally, many phosphors such as organic electroluminescence (EL) materials and inorganic EL materials have been put to practical use. However, these phosphors are mainly deteriorated in crystallinity due to oxidation and moistening, and deterioration of fluorescence characteristics over time. It is remarkable. Industrial products using such short-lived phosphors are familiar to mass-consumption societies that require single use, but are problematic from the viewpoint of resource saving. In addition, when applying the phosphor to illumination, a light source, or a display, it is indispensable to realize low voltage driving from the viewpoint of energy saving. On the other hand, although not yet put into practical use, some oxide polycrystals are known which have both fluorescence characteristics and robust chemical stability. Furthermore, it has been clarified that when an oxide phosphor is incorporated into an EL element as a high-quality thin film, it can be expected to be driven at a low voltage of about 10 V, unlike other inorganic EL materials. Also, a large area is required for general lighting and display applications.

  Therefore, in order to increase the sustainability of Japan's economy and society through energy saving and resource saving, there is an urgent need to develop a technology that can produce a high-quality oxide fluorescent thin film having a fluorescent property that can withstand practical use in a large area. A polycrystalline thin film composed of a set of three-dimensionally random crystals exhibits fluorescence characteristics but has very low intensity. Therefore, it is necessary to obtain high-intensity fluorescence by growing an alignment film having high crystallinity. In addition, since oxide phosphors are highly transparent, they are expected to be used as displays using windows. To achieve this, an oxide phosphor thin film is created on a transparent and inexpensive substrate. There is a need to.

Patent Document 1 discloses a method for manufacturing a thin film that emits light by applying a mechanical external force to a material containing a rare earth metal ion or a transition metal ion in an inorganic base material.
Patent Document 2 shows fluorescence characteristics of a polycrystalline Sn perovskite oxide system.
In Patent Document 3, a thin film is formed on a substrate by epitaxial growth at a temperature of 600 ° C. or more and 800 ° C. or less by a pulse laser deposition method as a polycrystalline target material in which an aluminum element is replaced with a perovskite on a SrTiO ₃ single crystal substrate. An oxide fluorescent epitaxial thin film is shown.
In Patent Document 4, a thin film is formed on a substrate by epitaxial growth at a temperature of 600 ° C. or higher and 800 ° C. or lower by a pulse laser deposition method using an oxide fluorescent material as a target material. An oxide fluorescent epitaxial thin film having improved fluorescence characteristics by heat treatment at 900 ° C. to 1200 ° C. is shown.
In Patent Document 5, a nanosheet is adsorbed on a solid substrate as a seed layer, and an oxide fluorescent alignment film is produced thereon, and red is obtained from the three primary colors of red, green, and blue, which are the basis of display production. The perovskite fluorescent thin film is shown.
Patent Document 6 discloses a method for producing a clay film comprising a step of forming a liquid film of a clay dispersion liquid containing a dispersion medium containing water and synthetic clay, and a drying step of removing the dispersion medium from the liquid film. Shows a method that can reduce the haze (cloudiness) of the resulting clay film even if the solid concentration of the clay dispersion is increased in order to shorten the time required for the drying step.

Non-Patent Document 1 shows that blue fluorescence can be obtained in a polycrystalline Sn-based layered perovskite structure.
Non-Patent Document 2 shows that fluorescence characteristics can be obtained when polycrystal CaSnO ₃ is substituted with Tb.
Non-Patent Document 3 shows that red fluorescent characteristics can be obtained with a polycrystalline layered perovskite Sr _{n + 1} TiO _{3n + 1} system.
Non-Patent Document 4 shows that blue-white fluorescence can be obtained by oxygen vacancies in SrTiO ₃ single crystals and thin films.
Non-Patent Document 5 shows that red fluorescence characteristics can be obtained by substituting Pr atoms for polycrystalline SrTiO ₃ .
Non-Patent Document 6 shows that red fluorescence characteristics can be obtained in polycrystalline Pr atom substitution (Ca _x Sr _1-x ) TiO ₃ .

JP-A-11-219601 JP 2007-146102 A JP 2009-155376 A JP 2008-19317 A Japanese Patent Application No. 2009-141730 JP 2008-137828 A

J. Mater. Sci. Lett., Vol. 11, 1330 (1992) Materials Chemistry and Physics Vol.93, pp.129-132 (2005) J.J.Appl.Phys.Vol.44, pp.761-764 (2005) Nature Materials Vol4,816 (2005) Appl.Phy.Lett Vol 78,655 (2001) Chem. Mater. Vol 17,3200 (2005)

  As shown in the above document, it is known that a good phosphor can be obtained in an oxide polycrystal, but it still emits three primary colors of red, green, and blue, which are necessary for manufacturing a display. No oxide fluorescent epitaxial thin film is known. In particular, the development of thin-film EL is indispensable for display applications, and the development of oxide fluorescent epitaxial thin films on solid substrates such as quartz is underway. The production of a display that focuses on the formation of an oxide fluorescent epitaxial thin film on a substrate having the same has not yet been developed.

  The object of the present invention is to provide a red color which is the basis for display production on a heat-resistant clay-based flexible sheet base material, which is different from a conventional solid substrate such as quartz, and is a perovskite. It is an object to provide a perovskite oxide fluorescent thin film body capable of forming a type oxide fluorescent thin film at low cost.

The present invention employs the following means in order to solve the above problems.
The first means includes a heat-resistant clay-based flexible sheet substrate, a gold thin film formed on the heat-resistant clay-based flexible sheet substrate, a nanosheet adsorbed on the gold thin film, Perovskite-type oxidation consisting of (Sr _x Ca _1-x ) _1-y Pr _y TiO ₃ : 0 ≤ x ≤ 0.8, 0.001 ≤ y ≤ 0.01 by vapor phase epitaxy on nanosheets It is a perovskite oxide fluorescent thin film characterized in that a fluorescent material thin film is formed.
The second means is that, in the first means, the nanosheet is [Ca ₂ Nb ₃ O ₁₀ ] − (CNO) nanosheet and [N (C ₁₈ H ₃₇ ) ₂ (CH ₃ ) ₂ ] + (DOA) nanosheet. A perovskite oxide fluorescent thin film characterized in that it is a composite LB film comprising:
A third means is the perovskite oxide fluorescent thin film characterized in that, in the first means or the second means, the heat-resistant clay-based flexible sheet base material is Claist (registered trademark). Is the body.
A fourth means is the perovskite oxide fluorescent thin film body according to any one of the first means to the third means, wherein the size of one side of the nanosheet is 10 nm or more and 10 μm or less. is there.

  According to the present invention, a perovskite oxide fluorescent thin film having excellent red fluorescence characteristics can be obtained on a flexible sheet-like substrate. As a result, development of an electroluminescence device using a perovskite oxide thin film on a flexible sheet-like substrate is expected. Furthermore, an electroluminescent device in which a perovskite oxide fluorescent thin film is formed on a flexible sheet-like substrate with a gold thin film as a lower electrode can be driven at a low voltage, and thus the system can be miniaturized. Furthermore, by using a perovskite oxide fluorescent thin film, a perovskite oxide fluorescent thin film having an advantage that the deterioration of crystallinity due to exposure of the sample to the atmosphere is extremely small can be obtained.

It is a figure which shows the perovskite type oxide fluorescent thin film body in which the perovskite type oxide fluorescent thin film was formed on the heat-resistant clayey flexible sheet base material which concerns on this invention. (Sr _x Ca _1-x ) _1-y Pr _y TiO ₃ : 0 ≦ x ≦ 0.8, 0.001 ≦ y ≦ 0.01 (X = 0.4, y = 0.002) as a target material by pulse laser deposition method, 700 ° C. It is a graph which shows the X-ray-diffraction pattern at the time of film-forming growth. Heat-resistant clay-based flexible sheet base material temperature of 700 ° C. by pulse laser deposition method (Sr _x Ca _1-x ) _1-y Pr _y TiO ₃ : 0 ≦ x ≦ 0.8, 0.001 ≦ y ≦ 0.01 (X = 4 is a graph showing fluorescence characteristics (excitation wavelength: 330 nm) when 0.4, y = 0.002) is formed.

An embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram showing a schematic configuration of a perovskite oxide fluorescent thin film according to this embodiment.
As shown in the figure, this perovskite oxide fluorescent thin film body 1 is formed by forming a gold thin film 3 as a lower electrode on a heat-resistant clay-based flexible sheet base material 2. The nanosheet 4 matching the lattice constant of the perovskite oxide fluorescent thin film 5 is adsorbed thereon, and the perovskite oxide fluorescent thin film 5 is formed thereon.

As the clay-based flexible sheet base material 2 having heat resistance, for example, Claist (registered trademark) made of a film-like mineral base material made of silicate clay is suitable. The heat-resistant temperature of the crater is 700 ° C. or higher, and it can be used as a soft substrate. Since high crystallinity cannot be expected even if the film is formed directly on the creest base material, high crystallinity of the perovskite oxide fluorescent thin film 5 is achieved by achieving lattice matching between the perovskite oxide fluorescent thin film 5 and the nanosheet 4. . Moreover, when producing an electroluminescent element, a lower electrode is required. Therefore, a gold thin film 3 that can be easily formed as a lower electrode and is excellent in chemical stability is formed on the clay-like flexible sheet substrate 2, and the lattice constant of the perovskite oxide fluorescent thin film 5 is formed on the gold thin film 3. The aligned nanosheet 4 is adsorbed. Nanosheet 4 is a composite LB film (Langmuir-Blodgett film) composed of [Ca ₂ Nb ₃ O ₁₀ ] ⁻ (CNO) nanosheet and [N (C ₁₈ H ₃₇ ) ₂ (CH ₃ ) ₂ ] ⁺ (DOA) nanosheet. It is deposited on the gold thin film 3 in advance. The lattice constant of the nanosheet material 4 is around 0.39 nm, and many materials of perovskite oxide have a lattice constant in the vicinity thereof. By setting it in this numerical range, it is possible to epitaxially grow a perovskite oxide fluorescent thin film with improved consistency and excellent crystallinity.

Details of the film forming method of the present invention will be described below. The perovskite oxide fluorescent thin film 5 was formed on the nanosheet 4 by a pulse laser deposition method. The laser irradiation frequency is 8 Hz, and the film formation time is 30 minutes. Further, the distance between the heat-resistant clay-based flexible sheet substrate 2 and the target was 30 mm. The laser energy density is about 1 J / cm ² during target irradiation. Since the perovskite oxide fluorescent thin film 5 can be formed in an oxygen stream, the deterioration of electrical characteristics and fluorescent characteristics due to oxygen deficiency or the like can be extremely reduced during oxide thin film growth. In the pulsed laser deposition method, a target material made of oxide is irradiated with an ArF (wavelength: 193 nm) excimer laser in low-pressure oxygen of 1 Torr or less, and the target material is turned into plasma to generate a plume, which faces the target material. In this method, a superheated substrate is placed on the surface and a thin film is deposited. Cluster growth is dominant at temperatures below 1000 ° C., and the target material can be deposited with its stoichiometric composition.

FIG. 2 shows a case in which a nanosheet 4 is adsorbed on a gold thin film 3 on a heat-resistant clay-based flexible sheet base material 2 produced in the present invention, and (Sr _x Ca _1-x ) _{1-y is} used as a target material. X-ray diffraction of the perovskite oxide phosphor thin film 1 during growth at 700 ° C. by Pr laser using the Pr _y TiO ₃ : 0 ≦ x ≦ 0.8, 0.001 ≦ y ≦ 0.01 (X = 0.4, y = 0.002) It is a graph which shows the result.
As shown in the figure, the peak that appears when 2θ is 30 degrees or less is a peak derived from the crust used as the heat-resistant clay-based flexible sheet substrate 2. PCSTO in the figure _{(Sr x Ca 1-x)} 1-y Pr y TiO 3: stands for 0 ≦ x ≦ 0.8,0.001 ≦ y ≦ 0.01 (X = 0.4, y = 0.002).

The production of the perovskite oxide fluorescent thin film 5 according to the present invention is the chemical composition of the perovskite oxide fluorescent thin film 5 (Sr _x Ca _1-x ) _1-y Pr, which is considered to obtain the best fluorescence characteristics. _y TiO ₃ : Film formation was performed at a substrate temperature of 600 ° C. and 700 ° C. at x = 0.4 and y = 0.002 where 0 ≦ x ≦ 0.8 and 0.001 ≦ y ≦ 0.01.

FIG. 3 shows a typical example of the investigation of the fluorescence characteristics of the thin film when the perovskite oxide fluorescent thin film 5 is formed at a temperature of 600 ° C. and 700 ° C. of the clay-like flexible sheet base material 2 having heat resistance. It is a graph which shows the fluorescence characteristic (excitation wavelength 330nm) when forming into a film with the temperature of the base material 2 at 700 degreeC.
As shown in the figure, the fluorescence characteristic is obtained at a wavelength of 615 nm, and it can be seen that the color is red. Presuming that these results were obtained with an optimal chemical composition, (Sr _x Ca _1-x ) _1-y Pr _y TiO ₃ : 0 ≦ x ≦ 0.8, 0.001 ≦ y ≦ 0.01 It is considered that fluorescence characteristics can be obtained.

DESCRIPTION OF SYMBOLS 1 Perovskite type oxide fluorescent thin film 2 Clay-like flexible sheet base material having heat resistance 3 Gold thin film 4 Nanosheet 5 Perovskite type oxide fluorescent thin film

Claims (4)

Heat-resistant clay-based flexible sheet substrate, gold thin film formed on the heat-resistant clay-based flexible sheet substrate, nanosheet adsorbed on the gold thin film, and vapor phase growth on the nanosheet The perovskite oxide fluorescent thin film consisting of (Sr _x Ca _1-x ) _1-y Pr _y TiO ₃ : 0 ≦ x ≦ 0.8 and 0.001 ≦ y ≦ 0.01 is formed at a temperature between 500 ° C. and 700 ° C. A perovskite-type oxide phosphor thin film characterized in that: The nanosheet is a composite LB film composed of [Ca ₂ Nb ₃ O ₁₀ ] − (CNO) nanosheet and [N (C ₁₈ H ₃₇ ) ₂ (CH ₃ ) ₂ ] + (DOA) nanosheet. The perovskite oxide fluorescent thin film body according to claim 1.   The perovskite oxide fluorescent thin film according to claim 1 or 2, wherein the heat-resistant clay-based flexible sheet base material is Claist (registered trademark).   The perovskite oxide phosphor thin film according to any one of claims 1 to 3, wherein a size of one side of the nanosheet is 10 nm or more and 10 µm or less.